Title of Invention	"A METHOD FOR PREPARING HIGHLY SULFURIZED METAL DITHIOCARBAMATES"
Abstract	A process is provided for the manufacture of highly sulfurized metal dithiocarbamates, such as molybdenum dithiocarbamate. A metal source, water and a reagent amine are heated under pressure with carbon disulfide.

Full Text

BACKGROUND OF THE INVENTION The invention relates to a proeess for preparing highly sulfuri/ed molybdenum dithioearbamates. Conventional sulfuri/ed molybdenum dithiocarbamates are known for use in lubricating formulations, and are currently used as additives in lubricating oils for imparting antifriction and antiwear properties, as well as extreme pressure and antioxidant properties. These compounds have the general structure (Structure Removed) where x 2.35-3 and, therefore, are not highly sulfuri/ed. It is also known to increase the sulfur to oxygen ratio in this structure (Structure Removed) where x 0.75 to 2.1 and R1 and R". which arc the same or different, arc hydrocarbyl groups containing 1 to 24 carbon atoms. Such higher sulfur compositions arc prepared from a sulfide compound such as alkaline metal hydrogen sulfides, ammonium hydrogen sulfide, alkaline metal sulfides, ammonium sulfide and mixtures thereof as taught in US 4098705. There is a desire for the dithioearbamates to have higher sulfur content (higher sulfuri/ed). With sulfur being an antioxidant, these compounds have better antioxidant stability afforded by the increased sulfur content. Very high sulfur levels have been found to produce copper corrosion, but levels of up to about three sulfur atoms on the molybdenum core of structure (Structure Removed) where x > 1.0. are acceptable High sulfur content (wherein sulfur replaces oxygen) affords an internal antioxidant at the molecular level, which provides an increased stability to the molecule, which is believed to afford improved antifriction retention properties in their application. The known preparation methods for the higher sulfuri/ed molybdenum dithiocarbamates involve the use of hydrogen sulfide or other sulfide during preparation to exchange oxygen-bound molybdenum to sulfur-bound molybdenum. The drawback of this process is the use of hydrogen sulfide or sources thereof, e.g. alkaline metal sulfides, ammonium sulfide and alkaline metal hydrogen sulfides, due to the danger and difficulty of handling these highly toxic materials. SUMMARY OF THE INVENTION The invention is an improved method to prepare high-sulfuri/cd molybdenum dithioearbamate compositions by using additional carbon disulfide in place of hydrogen sulfide (or a source thereof, e.g. sodium sulfide) as a sulfurization source. It has been unexpectedly discovered that under certain specific conditions, carbon disulfide can function as a reagent that will sulfurizc molybdenum dithiocarbamatcs, acting as a source to exchange oxygen bound to molybdenum with sulfur, with the production of carbon dioxide as the by-product. It is also expected that the process will prepare high-sulfurizcd dithiocarbamatcs of transition metals with valances of + 3 or higher, such as tungsten, chromium, manganese, iron, cobalt, nickel, etc. The inventive process results in several important advantages over the prior art process: a simpler and safer process without the need to use H2S or sources thereof; a more economical process because less expensive CS2 is used in place of H2S or sources thereof; and, as demonstrated below, a shorter total process time, at least with respect to liquid MoDTCs. DETAILED DESCRIPTION OF THE INVENTION Molybdenum dithiocarbamatcs arc complexes of an inorganic core and dithioearbamic acid. Bridged ("di-nuclear") or single molybdenum ("mono-nuclear") cores have been theorized. Additionally, coordination spaces on the molybdenum core may be filled with free amine or other coordinating moieties. This invention relates to a previously unknown method to prepare higher sulfurized versions of the existing dithioearbamate technology. The precise structure of the resulting compounds is not known. 1 Iowever it is believed that the inventive compositions arc molybdenum dithiocarbamatcs having the following general structure: We claim 1. A method for preparing highly sulfurized metal dithiocarbamates, comprising the steps of: (a) reacting a metal source, water, and at least one reagent amine; (b) removing the water from the reactor; (c) introducing carbon disulfide to the reactor, (d) reacting the contents of the reactor under pressure of between 13790-275792 Pa. at a temperature above the normal boiling point of carbon disulfide. 2. The method as claimed in claim 1, wherein the metal is a transition metal with valance of 1-3 or higher. 3. The method as claimed in claim 2, wherein the metal is molybdenum. 4. The method as claimed in claim 1, wherein the metal source, the water and the reagent amine arc heated together in step (a) at least half an hour as all solids have dissolved. 5. The method as claimed in claim 4, further comprising the step of, prior to the introduction of carbon disulfide in step (c), cooling the reactor contents. 6. The method as claimed in claim 4, for producing a liquid metal dithiocarbamate, further comprising the steps of, prior to the introduction of carbon disulfide in step (c), scaling the reactor, cooling the reactor contents to below 54°C (130°F), and evacuating the reactor. 7. The method as claimed in claim 4, for producing a solid metal dithiocarbamate. further comprising the steps of, prior to the introduction of carbon disulfide in step (c), sealing the reactor and cooling the reactor contents to below 37.8°C (100°F). 8. The method as claimed in claim 6, further comprising the steps of, prior to the sealing step, cooling the reactor contents to below 93.3°C (200°F) and adding process oil sufficient to reduce viscosity. 9. The method as claimed in claim 6, further comprising the step of, following the introduction of carbon disulfide, heating the reactor contents under pressure to achieve a desired reflux temperature at which a highly sulfurizcd metal dithiocarbamatc is formed. 10. The method as claimed in claim 9, wherein the reflux temperature is in the range of 107-135°C (225-275°F). 11. The method as claimed in claim 10, further comprising the step of, after completion of reflux, stripping off un-reacted carbon disulfide. 12. The method as claimed in claim 7, further comprising the step of, following the introduction of carbon disulfide, heating the reactor contents under pressure to achieve a desired reflux temperature at which a highly sulfurizcd metal dithiocarbamatc is formed. 13. The method as claimed in claim 12, wherein the reflux temperature is in the range of 121-138°C (250-280°F). 14. The method as claimed in claim 13, wherein the temperature of the reactor contents is slowly increased to reflux temperature over 2 hours, with a pressure-release valve of the reactor set at the maximum desired pressure. 15. The method as claimed in claim 11, further comprising the step of, after stripping, applying a vacuum to the reactor and heating the reactor contents at temperature in the range of 141-157°C (285-315°F) to remove any remaining carbon disulfide and water. 16. The method as claimed in claim 12, further comprising the step of, after completion of reflux, stripping off un-rcacted carbon disulfide. 17. The method as claimed in claim 3, wherein the molar ratio of reagent amine : molybdenum is in the range of 1.0-2.1:1.0. 1 8. The method as claimed in claim 17, wherein the molar ratio of reagent amine : molybdenum is in the range of 1.0-1.1:1.0 19. The method as claimed in claim 4, wherein the molar ratio of carbon disulfide : molybdenum is in the range of 2.1-3.5:1.0. 20. The method as claimed in claim 19, wherein the molar ratio of carbon disulfide : molybdenum is in the range of 2.2-3.0:1.0. 21. The method as claimed in claim 20, wherein the molar ratio of carbon disulfide : molybdenum is in the range of 2.3-2.5:1.0. 22. The method as claimed in claim 3, wherein the molybdenum source is selected from among molybdenum trioxide, molybdic acid and ammonium molybdate. 23. The method as claimed in claim 22, wherein the molybdenum source is molybdenum trioxide. 24. The method as claimed in claim 1, wherein the reagent amine is selected from one or more symmetric or asymmetric dialkylamines where R1 and R2. and R3 and R4 in a case where two different amines are used, are either identical or dissimilar, or mixtures thereof, and R1, R2, R3 and R4 arc independently selected from straight or branched chain, saturated or unsaturated alkyl groups of 1 to 40 carbon atoms, cycloalkyl groups of 6 to 40 carbon atoms, alkylcycloalkyl groups of 7 to 40 carbon atoms, aryl groups of 6 to 40 carbon atoms, arylalkyl groups of 7 to 40 carbon atoms, where the alkyl and aryl groups may be substituted with hcteroatoms or with other hctcroatom-containing groups and preferably from branched or straight chain, saturated or unsaturated alkyl or hctcroatom-containing alkyl groups containing 2 to 24 carbon atoms. 25. The method as claimed in claim 1, wherein an excess of carbon disulfide is added.

Documents:

2847-DELNP-2008-Abstract-(05-03-2012).pdf

2847-DELNP-2008-Claims-(05-03-2012).pdf

2847-DELNP-2008-Correspondence Others-(05-03-2012).pdf

2847-DELNP-2008-Correspondence Others-(16-01-2012).pdf

2847-DELNP-2008-Description (Complete)-(05-03-2012).pdf

2847-DELNP-2008-Form-1-(05-03-2012).pdf

2847-DELNP-2008-Form-13-(05-03-2012).pdf

2847-DELNP-2008-Form-2-(05-03-2012).pdf

2847-DELNP-2008-Form-3-(16-01-2012).pdf

2847-DELNP-2008-GPA-(05-03-2012).pdf

Correspondence Others-(05-03-2012).tif

Form-1.pdf

Form-3.pdf

Form-5.pdf